In the commercial natural gas production industry, a network of gas collection pipes often will connect and branch together tens to hundreds of natural gas ground wells in a localized geographic region. The individual wells will feed natural gas through the network of gas collection pipes to a common output location. The wells may be owned by several different land owners and/or mineral rights owners who may sell their natural gas production to a commercial supplier of natural gas. The commercial supplier will typically purchase natural gas from the land or rights owners based upon its needs. This provides a need for regulating and monitoring natural gas production from each well. Even if the commercial purchaser of natural gas owns the land or the mineral rights, it will still want to monitor and/or regulate the production of each well to control its supply. Often, the desired natural gas output is less than the maximum production capacity of the several wells combined. Such demands can change due to cyclical seasonal trends and for other economic reasons.
To regulate the production output of each individual well, the branch collection pipe for each individual well typically has a flow regulating valve and a gas flow sensor arranged in fluid series. The gas flow sensor indicates the amount of natural gas that flows through the collection pipe. The regulating control valve provides a variable degree of opening that forms a restriction orifice in the collection pipe and thereby sets the natural gas flow rate in the collection pipe.
By virtue of where natural gas deposits are geographically located, groups of natural gas production wells are often located in remote areas where there is no commercial supply of electricity. Such wells may also be distant or not readily accessible from civilization. As a result, achieving automatic control and actuation of gas regulating valves has not had straightforward solutions. Fluid pressure in natural gas production wells can be as high as about 900 psi or in some instances higher and as low as about 10 psi. This requires or necessitates an actuating means that has a high actuating force as wellhead regulating valves may therefore have hundreds of pounds of force exerted upon them. The ready answer in the prior art has been to use a small portion of the process gas (such as the natural gas) as working fluid to power a combination of pneumatic regulator/actuator components including a pneumatic actuator, I/P regulator, pressure reducing regulators and a positioner, that are arranged in an operational fluid network for positioning the regulating well-head valve, as shown schematically in FIG. 22 which depicts the typical wellhead production well system currently employed. In this arrangement, working fluid flow must be controlled. A solar panel and battery (which are kept as small as possible for costs reasons) are frequently employed to provide a small electrical local power source to power a motor operated regulator that electrical controls working fluid flow. This provides for electrical control over the pneumatic actuator.
Although pneumatic actuation has proven to work, there have long been several significant drawbacks using pneumatic actuation such as shown in FIG. 21. In particular, pneumatic actuating systems of the prior art (including many of the individual regulator and actuator components) both consume and exhaust natural gas, meaning that natural gas is therefore released gas into the atmosphere when the regulating valve is repositioned or otherwise controlled. Because of the discharge of gas, these systems may pose difficulties in meeting strict environmental regulations relating to fugitive natural gas emissions. Further, there is a significant safety hazard with fugitive natural gas emissions. An electrical spark whether produced by lighting, other adjacent equipment or components (including control electronics), or by maintenance personnel or their equipment when working on the gas network (which maybe increased when safety precautions are not followed), can potentially ignite the releases of natural gas and cause a potentially explosive situation.
In view of the foregoing, there has long been a need to provide a practical and economically feasible solution to reduce and if possible eliminate the hazards and other disadvantages associated with fugitive natural gas emissions that occur when controlling regulating valves for wellheads.